There are a variety of solar energy collector systems available for converting solar energy into other forms of energy that can be more readily used or stored. These systems typically employ solar collectors that collect solar radiation and convert it into a more useable form of energy, such as heat.
Solar collectors of the flat plate type have been used in low energy applications such as heating water, generating low pressure steam, supplementing air conditioning and heating systems, and the like. Flat plate collectors do not focus the sun's radiation and have limited applicability.
Another type of collector is generically called a concentrating collector. These collectors focus or concentrate the sun's radiation energy in a particular area. Concentrating collectors can be designed to operate at high temperatures with reasonable flow rates, thus substantially increasing the versatility of systems incorporating these collectors over systems employing flat plate collectors.
One type of concentrating collector is the parabolic trough collector. This type of collector uses an elongated reflective trough having a parabolic cross-section to concentrate the sun's radiation along a longitudinal focal line extending through the focal points of the parabolic elements of the trough. A conduit can be positioned along this longitudinal focal line and a heat transfer liquid can be circulated through the conduit, where it will be heated by the sun's energy. Satisfactory flow rates at high temperatures can be obtained from these collectors.
With the assistance of a tracking system, parabolic trough collectors can become very efficient as they follow the movement of the sun. U.S. Pat. No. 6,886,339 discloses a solar power collection system comprising parabolic trough collectors that operate with a positioning system that provides movement about a single axis of rotation. A controller drives a motor to pivot the parabolic trough collectors about the longitudinal focal line. However, because of the need for such a tracking system, parabolic trough collectors have typically relied on complicated and expensive rotating assemblies to position the parabolic trough collectors directly toward the sun as the sun travels from east to west during the day. Consequently, there is a need for a solar energy collector system that does not rely on complicated and expensive rotating assemblies to position the parabolic trough collectors directly toward the sun.
Another problem associated with solar energy collector systems is with respect to the conduit positioned along the focal line. A small focal point is desired to maximize the efficiency of the collectors. However, this typically requires regular adjustments of the reflecting surfaces. A tradeoff is to use a larger focal point to collect more energy, but this reduces efficiency since a larger volume of liquid is to be heated. Consequently, there is also a need to improve the efficiency of the conduit for solar energy collector systems.